1. Field of the Invention
The present invention relates to an ink jet recording apparatus and an ink suction method of the recording head.
Specifically, the present invention relates to an ink jet recording apparatus provided with a recording head which is moved in the direction of the width of a recording paper for printing an image on the recording paper by jetting an ink droplet toward the recording paper based upon print data and more, particularly relates to an ink jet recording apparatus wherein ink is prevented from being dry and being clogged by forming the capping device so that the capping device has a specific structure, the printing of a dot is never omitted and color mixture and mottled color are prevented in color printing, and an ink suction method of the recording head in flushing and cleaning.
2. Description of the Related Art
As graphic processing can be relatively easily executed owing to the development of a personal computer, a recording apparatus which enables the output of a high quality hard copy of a color image on a display is desired.
A recording apparatus in which an ink jet recording head is mounted to meet such a request is provided.
As in such an ink jet recording apparatus, noise in printing is relatively small and a small dot can be formed in high density, it is used for multiple types of printing including color printing.
Such an ink jet recording apparatus is provided with an ink jet recording head to which ink is supplied from ink storage means and paper feed means for relatively moving recording paper to the recording head so as to record by jetting an ink droplet on recording paper, moving the recording head according to a printing signal and forming dots.
A recording head which enables the jetting of black, yellow, cyan and magenta ink is provided to a common head holder and enables not only the printing of a text by black ink but full color printing by changing the ratio in which each ink is jetted. As such an ink jet recording head prints by jetting ink pressurized in a pressure generating chamber on recording paper from a nozzle as an ink droplet, there is a problem that a nozzle aperture is clogged due to the increase of the viscosity of ink and the solidification of ink respectively caused by the evaporation of a solvent from a nozzle aperture, the adhesion of dust, further, the mixture of a bubble and others and as a result, the failure of printing occurs.
Therefore, an ink jet recording apparatus is normally provided with a capping device for sealing a nozzle aperture of the recording head while the ink jet recording apparatus is not used and cleaning means for cleaning a nozzle plate if necessary.
The capping device not only functions as a cap for preventing ink from being dry at a nozzle aperture but is provided with a function for sealing a nozzle plate by a cap member, sucking ink from a nozzle aperture by negative pressure from a suction pump and solving the clogging of the nozzle aperture if the nozzle aperture is clogged.
Processing for compulsorily exhausting ink executed to solve the clogging of a recording head is normally called cleaning, is executed in case printing is restarted after longtime cessation and in case a user presses a cleaning switch to solve the clogging of a recording head and is processing for wiping by a cleaning member formed of an elastic plate such as rubber after an ink droplet is jetted.
A function for applying a driving signal not related to printing to a recording head so as to jet an ink droplet is also provided, is normally called flushing and is operation executed every fixed cycle to recover an uneven meniscus in the vicinity of a nozzle aperture of a head by wiping and others in cleaning and to prevent a nozzle aperture which hardly jets an ink droplet in printing from being clogged.
FIG. 12 is a sectional view showing the schematic constitution of a capping device used for a conventional type ink jet recording apparatus and shows a state in which ink is sucked from a recording head by a cap unit constituting the capping device. FIG. 13 shows a state of the cap unit when it is viewed from the top.
A cap unit 38 is constituted by a rectangular cap case 40 the top face of which is open and a cap member 16 housed in the cap case 40 and formed of flexible material and the cap member 16 is formed with the upper edge slightly protruded from the cap case 40.
An ink absorber 17 formed by porous material is housed at the inner bottom of the cap member 16.
An ink suction port 18 and an atmospheric air open port 19 in most apparatuses are arranged through the cap case 40 and the cap member 16 at the bottom of the cap case 40 and the cap member 16.
The above ink suction port 18 and the atmospheric air open port 19 are arranged so that they are located at a predetermined interval approximately along the center in the longitudinal direction of the capping device when the capping device is viewed from the top as shown in FIG. 13.
In the meantime, a reference number 8 denotes a recording head for color, the recording head 8 is located over the capping device and a nozzle plate 14 is capped by the capping device.
A nozzle aperture 15 is arranged in the nozzle plate 14 and is constituted so that yellow, cyan and magenta ink is jetted by the action of a piezoelectric vibrator 13 arranged corresponding to each nozzle aperture 15.
In the above constitution, ink suction action for solving the clogging of a nozzle aperture is executed by operating a suction pump connected to the ink suction port 18 of the cap member with the cap member 16 closely touched to the nozzle plate 14 of the recording head 8 as shown in FIG. 12 and applying negative pressure to the inside of the cap.
Ink is jetted from the nozzle aperture 15, the atmospheric air flows in from the atmospheric air open port 19 when negative pressure inside the cap is reduced to some extent and negative pressure inside the cap is all released.
However, in the conventional type constitution shown in FIGS. 12 and 13, as the atmospheric air open port 19 is provided under the cap, ink is left at the end of the atmospheric air open port 19 after ink is sucked.
Further, as a sheet formed of porous material is normally used for the ink absorber 17 provided inside the cap, ink bubbles are blown up because opening to the atmospheric air is executed through such an ink absorber.
When such ink bubbles are scattered and adhere to the nozzle aperture 15, color mixture and the failure of printing in a dot occur.
To solve such problems, technique disclosed in Japanese Patent Publication No. Hei. 7-68766 for example for elastically deforming a cap by minutely moving a carriage on which a recording head is mounted or pulling the cap and executing opening to the atmospheric air from clearance made between a nozzle plate and the cap or technique for providing an atmospheric air open port on the surface of the nozzle plate of a recording head and executing opening to the atmospheric air from the side of the head is proposed.
However, as for the former technique, fatigue, distortion and others may occur in cap material due to long-term reciprocation, adhesion between a cap and a nozzle plate may be lost and the reliability of an apparatus is deteriorated.
Also, as for the latter technique, as a head is large-sized by providing an atmospheric air open port on the surface of a nozzle plate and a cap itself is further large-sized, there occurs a problem that the efficiency of suction is deteriorated.
As in a recent ink jet recording apparatus, the number of nozzle apertures constituting a recording head is increased to meet a request for high speed printing and high quality of color printing and as a result, the recording head has a tendency to be large-sized.
Therefore, a cap unit of a capping device for sealing the recording head is also necessarily large-sized, large unbalance occurs in negative pressure to act because of the increase of distance between the ink suction port 18 communicating with a suction pump and the nozzle aperture 15 and ink is difficult to uniformly jet from all nozzle apertures constituting the recording head.
To partly solve such problems, a flow regulating plate for positively changing the resistance of a passage for leading exhausted ink corresponding to distance from an ink suction port is inserted as disclosed in Japanese Patent Publication No. Hei. 7-195712 for example and to promptly and securely exhaust ink into a cap member outside without scattering ink, a capping device provided with an atmospheric air communicating hole disclosed in Japanese Patent Publication No. Hei. 7-290723 and others are proposed, however, as these are provided to securely exhaust ink into a large-sized capping device outside and negative pressure to act on a nozzle aperture cannot be adjusted, ink cannot be uniformly jetted from any nozzle aperture and there is still left a problem that the mottled color and color mixture of printing caused by the above uneven jetting cannot be completely avoided.
The present invention is made to solve the above problems and a first object is to provide an ink jet recording apparatus in which a small-sized capping device which enables preventing color mixture and the failure of printing in a dot without scattering ink to the side of a nozzle plate when the inside of a cap is opened to the atmospheric air after ink is sucked is mounted.
The provision of an ink jet recording apparatus which simplifies the constitution of a valve for making an atmospheric air open port communicate with the atmospheric air and enables reducing the cost of the apparatus is added to the above object.
Further, a second object is to provide an ink jet recording apparatus which can uniformly apply negative pressure to a nozzle aperture when negative pressure is applied to a recording head and ink is compulsorily exhausted from a nozzle aperture of the recording head and in which the mottled color and color mixture of printing caused by the unbalance of negative pressure are completed avoided.
Further another object of the present invention is to provide an ink suction method from a recording head of a recording apparatus which is effective to prevent ink from bubbling in a capping device when ink is sucked and to prevent ink from adhering to a nozzle aperture.
According to the present invention, as an ink jet recording apparatus equivalent to a first embodiment to achieve the above objects, an ink jet recording apparatus in which a nozzle ink jet recording head provided with a nozzle plate provided with an aperture for jetting an ink droplet and a capping device provided with a cap unit for sealing the apertures of the nozzle plate when the recording apparatus is not used are mounted and which is characterized in that an ink suction port for supplying negative pressure for exhausting ink from a nozzle aperture if necessary is arranged at the bottom of the cap unit of the capping device while the apertures of the nozzle plate are sealed and an atmospheric air open port for releasing the negative pressure is arranged on its one side is provided.
Also, according to the present invention, as an ink jet recording apparatus equivalent to a second embodiment, an ink jet recording apparatus in which a nozzle ink jet recording head provided with a nozzle plate provided with an aperture for jetting an ink droplet and a capping device provided with a rectangular cap unit for sealing the apertures of the nozzle plate when the recording apparatus is not used are mounted and which is characterized in that an ink suction port for supplying negative pressure for exhausting ink from a nozzle aperture is arranged at the bottom of the cap unit of the capping device and a porous plate provided with plural through holes for adjusting the distribution of pressure in the longitudinal direction of the cap unit is housed between the inner bottom face of the cap unit and the upper open face is provided.
Further, according to the present invention, as an ink suction method of a recording head in an ink jet recording apparatus provided with an ink jet recording head for jetting an ink droplet corresponding to print data, capping means which selectively communicates with the atmospheric air and to which negative pressure from a suction pump is applied for sealing the recording head and gas suction means for supplying negative pressure to the capping means, an ink suction method of an ink jet recording head comprising a process for exhausting slight quantity of ink from the recording head and injecting the ink into the capping means, a process for sealing the recording head by the capping means and a process for applying negative pressure from the suction pump to the capping means and sucking ink from the recording head is provided.
The ink jet recording apparatus equivalent to the first embodiment of the present invention made to achieve the above object is an ink jet recording apparatus in which an ink jet recording head for jetting an ink droplet and a capping device provided with a capping unit for sealing nozzle apertures when the recording apparatus is not used and sucking ink from a nozzle aperture if necessary are mounted and is characterized remarkably in the constitution in that an atmospheric air open port for opening the inside of the cap unit to the atmospheric air is arranged on one side of the cap unit of the capping device.
In this case, it is desirable that an ink absorber is housed in the cap unit and the atmospheric air open port arranged on one side of the cap is located above the ink absorber.
It is desirable that the atmospheric air open port is formed so that the atmospheric air open port is tilted toward the ink absorber.
In a desirable embodiment, an ink suction port is arranged at the bottom on the other side opposite to one side on which the atmospheric air open port of the cap unit is arranged.
The cap unit is formed in a rectangle, the atmospheric air open port is arranged at a corner on one side of the cap unit and the ink suction port may be arranged at the bottom at a corner opposite to the atmospheric air open port diagonally.
Further, the capping device is constituted at least by a cap case and a cap member formed of flexible material, the cap member is formed so that it is protruded from the upper edge of the cap case, an atmospheric air open port pierced in the direction of the thickness of the cap member is provided to a part of the cap member protruded from the cap case and the atmospheric air open port is constituted so that it is closed or opened according to pressure of the cap member upon the recording head.
In this case, it is desirable that the upper edge of the cap member to which the atmospheric air open port is provided is protruded from the other part.
In an ink jet recording apparatus provided with the capping device constituted as described above, as the atmospheric air open port for opening the inside of the cap to the atmospheric air is arranged on one side of the cap, ink bubbles can be prevented from being generated in opening to the atmosphere and ink left at the end of the atmospheric air open port can be effectively prevented from being scattered on the side of a nozzle plate.
The flow of air is formed in opening to the atmospheric air and the flow of ink can be improved by arranging the ink suction port at the bottom on the other side opposite to one side on which the atmospheric air open port is arranged or arranging the ink suction port at the bottom at a corner opposite to the atmospheric air open port diagonally.
Further, the atmospheric air open port is closed or opened according to the pressure of the cap member upon the recording head by forming the atmospheric air open port so that it is pierced in the direction of the thickness of the cap member.
The ink jet recording apparatus equivalent to the second embodiment of the present invention is characterized remarkably in the constitution in that a porous plate provided with plural through holes for adjusting the distribution of pressure in the longitudinal direction of the cap is housed between the inner bottom face of the cap of the cap unit provided with the negative pressure supplying ink suction port in the capping device and the open face so as to adjust negative pressure applied to a nozzle aperture.
Hereby, as negative pressure from the ink suction port can be adjusted so that it uniformly acts upon any nozzle aperture independent of the length of the recording head and ink can be uniformly exhausted from any nozzle aperture, fine and visible printing and images without mottled color and color mixture can be stably provided even if multiple ink colors are provided and the recording head and the cap unit of the capping device for sealing the recording head are large-sized.
Further, a thin hole of an ink absorbing sheet housed in the capping means is sealed with ink beforehand, the capacity of space in the capping means is reduced and the inclusion of air can be reduced and bubbles can be prevented from being generated in sucking ink by using an ink suction method according to the present invention comprising a process for exhausting slight quantity of ink from the recording head and injecting ink into the capping means, a process for sealing the recording head by the capping means and a process for applying negative pressure from the suction pump to the capping means and sucking ink from the recording head.